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2. Contains Nitrogen.
Organic base.—If it is a base or amine, amino-phcnol or
amino-acid, it will probably dissolve in dilute hydrochloric acid
and yield a chloroplatinate with platinic chloride. Some
aromatic bases like diphenylamine are not very soluble in dilute
acids. Ammo-phenols and acids may be extracted with ether
from an acid solution to which ammonia has been added till
faintly acid and then sodium acetate. Many amines and
ammo-phenols give quinones on oxidation with potassium
bichromate and sulphuric acid having a characteristic smell
(p. 192). Many of the common alkaloids when dissolved in
hydrochloric acid (avoid excess) give a brown amorphous
precipitate with iodine solution and respond to other general
reactions for the alkaloids (see p. 320). To identify the
individual alkaloid, special tests must be applied.
Primary, secondary, and tertiary amines may be distinguished
as follows : To a solution of the base in dilute hydrochloric acid
add a few drops of sodium nitrite solution. In the case of
primary aliphatic amines, a rapid evolution of nitrogen will at
once occur; a primary aromatic amine at first gives a clear
solution of the diazonitim-salt, which evolves nitrogen and turns
darker on warming. The effervescence, due to the liberation of
nitrous fumes, is easily distinguished from that of nitrogen,
which goes on uninterruptedly, even when the liquid is removed
from the flame.
After the solution of the cliazonium salt has been decomposed
by warming, the phenol which has been produced may be
extracted with ether, the ether evaporated, and the phenol
identified by special tests. A solution of the diazonium salt,
when poured into a solution of/3-naphthol in caustic soda, will
usually give a red azo-colour. The original amine, if liquid, may
sometimes be identified by warming with a little acetyl chloride
and converting it into the solid, acetyl derivative, which is
recrystallisecl and the melting-point determined (see Reaction 3,
P. 76).
In the case of a secondary base, the above treatment with
hydrochloric acid and sodium nitrite will give an insoluble
nitrosamine (liquid or solid), which is frequently yellow. It may
be separatee! by ether and, after removing the ether, tested l*y
Liebermann's nitroso-reaction (see Reaction 3, p. 159). Nitrous
.acid has no action on tertiary aliphatic amines, but forms nitroso-